Intraocular lenses (IOLs) and other ophthalmic lenses have been configured to provide multiple foci, for example, to provide both distant vision and near vision to a subject, thus at least approximating the accommodative ability of the natural lens in a younger subject. Examples of such lenses are disclosed in U.S. Pat. No. 6,536,899 to Fiala; U.S. Pat. Nos. 5,225,858; 6,557,998; 6,814,439; 7,073,906 to Portney; U.S. Pat. No. 7,188,949 to Bandhauer; and U.S. Pat. No. 7,093,938 to Morris, all of which are herein incorporated by reference in their entirety.
Such multifocal or bifocal ophthalmic lenses may generally be classified as multifocal diffractive lenses or multifocal refractive lenses. Various advantages and disadvantages have been associated with each class or type of multifocal lens. One approach for incorporating the benefits of each class of multifocal lens is to use a multifocal diffractive lens in one eye and a multifocal refractive lens in the other eye.
A common problem with multifocal IOLs is that of halo patterns or images that can occur when an out-of-focus image associated with one of the foci is superimposed with an in-focus image associated with another focus of the lens. For example, a distant automobile headlight, when seen through a typical diffractive bifocal lens, appears as an in-focus spot on the retina of the eye and an out-of-focus blur spot surrounding the in-focus spot and having a distinct outer border. This distinct outer border has been found to be annoying to users and various efforts have been made to soften this border so that the halo spot is less noticeable.
Multifocal ophthalmic lenses are needed that incorporate the advantages of both multifocal diffractive and multifocal refractive intraocular lenses within a single optic in synergistic ways that enhance the optical performance over traditional multifocal lenses and/or reduce the effects of halo images.